EP0598780A1

EP0598780A1 - Surgical high-frequency generator for cutting tissues

Info

Publication number: EP0598780A1
Application number: EP92916955A
Authority: EP
Inventors: Heinz Lindenmeier; Georg Lohr; Karl Fastenmeier; Gerhard Flachenecker
Original assignee: Karl Storz SE and Co KG
Current assignee: Karl Storz SE and Co KG
Priority date: 1991-08-12
Filing date: 1992-08-12
Publication date: 1994-06-01
Anticipated expiration: 2012-08-12
Also published as: DE59209642D1; EP0598780B1; WO1993003677A2; US5749869A; WO1993003677A3

Abstract

Un générateur de haute fréquence utile en chirurgie pour inciser des tissus comprend des agencements de réglage qui permettent de régler au moins une des valeurs électriques momentanées initiales, telles que le courant, la tension, la puissance ou l'arc électrique. Afin d'améliorer la performance du dispositif d'incision, celui-ci comprend un générateur électronique de valeurs de consigne et un dispositif de mesure pourvu d'une unité d'évaluation afin de suivre directement et/ou indirectement l'incision. Le générateur électronique de valeurs de consigne établit au début de l'incision un réglage du générateur particulièrement approprié pour effectuer l'incision, maintient ces valeurs de consigne jusqu'à ce que le dispositif de mesure indique que la sonde a sectionné des tissus, puis fournit une valeur de consigne inférieure pour le générateur afin que celui-ci effectue une incision normale correspondant au but voulu de l'opération.A high frequency generator useful in surgery to incise tissue includes control arrangements which adjust at least one of the initial momentary electrical values, such as current, voltage, power, or electric arc. In order to improve the performance of the incision device, the latter comprises an electronic setpoint generator and a measuring device provided with an evaluation unit in order to directly and / or indirectly follow the incision. The electronic setpoint generator sets at the start of the incision a particularly suitable generator setting for making the incision, maintains these setpoints until the measuring device indicates that the probe has sectioned tissue, then provides a lower setpoint for the generator to make a normal cut corresponding to the intended purpose of the operation.

Description

High frequency surgical generator for cutting tissues

Description

Technical field

The invention relates to a high-frequency generator for high-frequency surgery according to the preamble of the independent claims 1, 7 and 13.

State of the art

High frequency currents are used in surgery to cut biological tissue or to coagulate, i.e. Blood breastfeeding used.

High-frequency currents are used in surgery to remove tissue parts particularly when the surgical site can be reached through natural openings in the body, but a scalpel cannot be attached without opening the patient's body. For example, in urology, transurethral surgical instruments and high-frequency currents can be used to remove tumors from the bladder or to remove pathological growths in the prostate. In enterology, for example, polyps can be separated from the intestinal wall in a similar way. The probe of the surgical instrument has a cutting effect only as long as the high-frequency generator supplying the high-frequency current is activated is. This ensures safe insertion and removal of the surgical instrument through the natural body openings.

Some of the generators customary today can be set electronically in at least one electrical output variable such as current, output voltage, power, open circuit voltage or internal resistance. With this setting, the output power can be influenced directly or indirectly. This output power must be set according to the surgical goal and the conditions at the surgical site.

A problem in high frequency surgery is the correct dosage of the currently applied high frequency power. The high-frequency power which is at least necessary for good cutting action can fluctuate greatly. It depends on the nature of the tissue, the conductivity and the water content of the tissue, the shape and size of the probe, the depth of cut and the speed of the cut, and other electrical parameters, all of which, in the course of an operation, involve certain, often very abrupt, changes are subject. The usual setting of the high-frequency generator, gained from the experience of the surgeon, therefore leads on average to a significantly excessive high-frequency power, the dangers of which the surgeon must consciously expose to his patient and himself. In order to be able to keep these dangers as small as possible or to be able to rule them out almost completely, the instantaneous output power of the high-frequency generator would have to be regulated automatically in such a way that it corresponds to the absolutely necessary minimum dimension at any time.

A particular problem here is the beginning of the cut. ^' Ever depending on the condition of the probe and the tissue, the initial conditions can vary widely. For example, the probe can be bare metal with a clean surface and therefore good conductivity. It can also be covered with an insulating oxide layer or carbonized tissue remnants after several cuts or coagulations. A high generator voltage is necessary to break through this layer. The decisive factor for the penetration of the insulating layer is the electrical field strength, which must be above the breakdown field strength of this layer. The generator must deliver a correspondingly high voltage.

The tissue itself can be changed by previous cuts or coagulations. Cutting is particularly difficult during operations on the stomach and intestines. Here the tissue surface is very moist and particularly good electrical conductor. Here too, cutting is only possible with a very high generator output. What is important here is a high power supply and thus a high generator current in order to evaporate the conductive liquid as quickly as possible.

If the power output of the generator is constant, the generator must be set by the operator so that it delivers at least the power necessary for cutting. As measurements in the laboratory and in clinics have shown, the power required for cutting is substantially higher than the power required to continue the cut. The surgeon will now continue the cut with an unchanged setting, accepting the known risks of excessive power output.

If a certain cutting is not possible, the energy supplied leads to a coagulation of the tissue surface. This makes it even more resistive and it is hardly possible to cut it in such a place.

At least a much higher power output of the generator is necessary for this.

A solution to the problem is described in German Patent 2504280. In this device, the extent of the arc between the probe and the tissue to be cut is determined with the aid of a display device and the electrical signal derived therefrom is fed to a control device. The control device compares this signal with the setpoint program of a setpoint generator and derives from it a controlled variable which adjusts the output current strength of the generator so that the intensity of the arc follows the setpoint program. With this regulation, the minimum power required for cutting is set at any moment. However, the technical effort involved in the implementation is considerable. A different solution is therefore necessary for simple and inexpensive HF surgical generators.

Another proposed solution is the device proposed in German laid-open specification DE 3420340. After the generator is switched on, it increases the power for a constant, preset time. As measurements in the laboratory and in clinics have shown, the energy required for cutting varies considerably. Increased power output over a given period of time rarely does justice to practice. In addition, when using this method, it is absolutely necessary that the probe rests on the tissue when the generator is switched on, since the increased power is immediate is released after switching on the generator. If the tissue is not touched until a short time after the generator has been switched on, the generator already delivers its normal cutting power and the device is no longer effective.

Further problems, but also special possibilities, arise in high-frequency surgery, if not only homogeneous tissue is available at the operation site, or even different types of materials are available at the operation site.

For example, in the case of prostate sections, the adenoma tissue to be peeled from the tissue of the prostate capsule, into which it is not allowed to cut Another example is cutting in the vicinity of large blood vessels. Here, a separation can often lead to bleeding that is difficult to treat. If the blood vessel can be recognized, the generator output can be reduced so that a cut is no longer possible. The vessel can be closed with a subsequent coagulation.

If the cutting electrode touches bone during a cut, it can be thermally damaged. The danger is particularly great in dentistry. Here it is easy to penetrate too deeply into the thin layer of gums and touch the jawbone. Therefore, these should also be recognized by the generator.

Particularly long-lasting negative effects of high-frequency surgery occur when the cutting electrode has metallically conductive parts in the patient's body, such as implants, screws, nails, dental fillings and crowns or else Operative instruments such as forceps, mirrors or shafts touched by resection instruments. The HF current flows from the cutting electrode over these metallic parts over a large area to the surrounding tissue. Large-area coagulation can occur at the transition points. European patent application 91100442.2 describes a device which limits the output current of the generator. This can sometimes reduce tissue damage that occurs when the cutting electrode touches metallic conductive parts in the body. The power that is delivered to the tissue when the current limitation is activated at the site of the operation is proportional to the real part of the impedance of the transition from the metallic conductive part to the surrounding tissue. The effectiveness of this device is therefore inversely proportional to the impedance of the tissue transition. In the case of small-area tissue transitions, the impedance is very high and thus the power loss implemented. It is precisely these small-area tissue transitions that can only be loaded with low output. This means that the most sensitive tissue areas are least protected by this protective device. This method is also only suitable for special applications, since the tissue impedance can fluctuate by more than an order of magnitude in conventional cuts without metal contact. This results from the large fluctuation range of the cutting parameters such as electrode cross-section, immersion depth of the cutting electrode, cutting speed and the arc that is always burning between the cutting electrode and tissue during cutting. With this method, there is a very high risk that insufficient current is available for a quick cut and that the surgeon is thus impeded. On the other hand, there is also the danger that metallic conductive parts will only touch the tissue over a small area. In this case it is Despite the current limitation, the power output is high and severe burns can result. The method fails completely if there is high-resistance tissue in the vicinity of the tissue to be cut, which must not be cut into, or which must not be thermally stressed.

Another problem in high frequency surgery is the disruption of other devices and equipment and the irritation of the patient's nerves and muscles. Various devices are affected by the high radio frequency power that is used in HF surgery. In this way, interference can couple inductively, capacitively or through radiation. Frequently, HF surgical generators do not emit a narrow-band signal at the fundamental frequency of the generator, but rather a wide spectrum in the range from a few Hz to several MHz due to steep rising edges and modulation. Even in the case of generators that primarily only output power on the fundamental wave, harmonics of the generator frequency arise when arcing occurs on the probe due to its non-linearities. This often affects or interferes with devices if they have not been designed to be particularly immune to interference. However, in general, the technical problems of the affected devices can be used to reduce the interference problems. Another possibility, specifically to minimize the effects of interference in images from video cameras, is described in European patent 0429204A1. The pulsed output signal of an HF surgery generator is synchronized with the signal of a video camera, so that the high-frequency interference caused by the generator only affects insignificant parts of the camera image. Blanking with such a high frequency produces an RF signal with a high crest factor, as is usually used for coagulation. Because of the coagulation it creates, low-necrosis cutting is not possible. Cutting without disruptive necrosis is only possible with blanking at frequencies below 1000 Hz.

A much more important effect is the impact on the patient's body. Although HF surgery is based on the thermal effects of the current, the electrical effects are not negligible. Signals with the usual generator frequencies above 300 kHz (according to VDE) do not cause any demonstrable irritation of muscles and nerves. However, the arcs that always occur during cutting also result in a component with a very low frequency close to 0, the 0th harmonic of the generator signal. This portion, which, as measurements have shown, can occur with amplitudes of up to a few volts, stimulates muscles and nerves. However, these are generally undesirable and often dangerous.

An energy of 10 J is enough to trigger the contraction of a muscle. These can lead to sudden, strong movements of the patient on the operating table. As a result, injuries to the patient can occur. However, irritation of the heart muscle is much more dangerous. Even short impulses with an energy of 400 Ws can lead to ventricular fibrillation. In this self-excited state, the heart muscle works so quickly that the blood throughput becomes very small and the body is no longer adequately supplied with blood. As a result, death occurs. Ventricular fibrillation can be eliminated in clinics with the help of a defillibrator. However, such a device is used in many applications of HF surgery, such as in small medical practices or in dentists not available.

There are several ways to avoid these dangerous side effects. The simplest is the avoidance of potentially dangerous operations such as in the heart region. Likewise, in potentially endangered patients such as those with pacemakers, the use of electrosurgical surgical techniques is generally avoided. Another way of reducing, if not ruling out, the risk is to minimize the power used for the electrosurgical operation. This also minimizes the dangerous low-frequency currents. This is e.g. possible with a device described in German Patent 2504280. It measures the intensity of the arc and supplies the patient with only the minimal energy required to maintain the arc required for cutting.

With many surgical techniques, HF surgery offers such significant advantages that use with potentially endangered patients in potentially endangered regions of the body should also be possible. Particularly gentle endoscopic interventions are particularly important in elderly patients who, however, wear pacemakers more frequently.

Presentation of the invention

It is therefore the task of improving a high-frequency generator for high-frequency surgery in such a way that undesirable side effects of any kind are excluded or at least sustainably reduced.

This applies in particular to the adaptation to the circumstances of the area of operation in such a way that a rapid and low coagulation cutting is achieved. Furthermore, the high-frequency generator according to the invention is intended to automatically recognize different materials, in particular also metallic conductive parts, and types of tissue in the vicinity of the cutting electrode, so that the performance of the generator can be adapted to the desired operating purpose.

A further requirement for the structure of the high-frequency generator is to minimize the interference with other devices or the potentially dangerous irritation of certain muscles and nerves.

This object is achieved according to the invention with the measures disclosed in the independent claims 1, 7 and 13. Developments of the invention are characterized in the subclaims.

With the aid of a measuring device for the indirect and / or immediate detection of the cutting, a high-frequency generator with control devices for setting the instantaneous electrical output variables is set by a setpoint generator. Immediately after the generator has been activated, the setpoint generator specifies a setpoint for a generator setting that is particularly suitable for cutting. Depending on the impedance conditions at the operating site, this can be an increased generator voltage, an increased generator current or an increased generator power. In accordance with the control characteristic of the generator, the setpoint can also be specified for another electrical variable corresponding to the power, such as voltage or current. A measuring device determines the beginning of the cutting of the probe. The probe cuts as soon as it is under a Separation of the cell structure penetrates into the tissue. In general, an arc occurs between the probe and the tissue at the same time. As soon as a cutting is detected, the setpoint generator specifies a lower setpoint for the generator, so that a cut can be carried out without undesired tissue coagulation. The mean power supply during a cut is thus significantly lower than with a constant generator setting at a value at which cutting is possible.

A particularly advantageous embodiment is that the measuring device determines a movement of the probe in the tissue for the indirect and / or immediate detection of the cutting. This can e.g. done by a distance measurement. If the probe sinks further into the tissue than a distance specified by a setpoint device, cutting is signaled.

A safe indicator of high frequency surgical cutting is the arc that occurs between the probe and the tissue. A further advantageous embodiment is therefore that the measuring device (2) determines the arc occurring on the probe for the indirect and / or immediate detection of the cutting. This can preferably be done by spectrally considering the generator output signal. For this purpose, a high-frequency generator for high-frequency surgery with a device for setting the maximum output power is controlled by the output signal of a display device and an evaluation circuit. The electrical power contained in at least two frequency ranges is used for control. The output signal of an auxiliary oscillator can optionally be Stungoszillatorsignal be additively superimposed. Now the mixed products that are caused by the arc can be evaluated and detected.

A detailed description of this solution variant is given in connection with the specific structure of the high-frequency generator for detecting different materials, see also claims 7 to 12.

Another characteristic of the beginning of the cut, as measurements have shown, is the increase in impedance between the probe and the tissue. This jump in impedance is particularly pronounced when cutting tissues in the stomach and intestines. Here the highly conductive liquid and mucus layer on the tissue surface must first be evaporated before cutting into the underlying tissue layers is possible. A further advantageous embodiment is therefore that the measuring device for the indirect and / or direct detection of the cutting evaluates the impedance between the probe and the neutral electrode. The output signal of the high-frequency generator or the output signal of an auxiliary generator can also be used for this.

Depending on the nature of the fabric, different generator settings are necessary for quick cutting. Therefore, an advantageous embodiment consists in the fact that a setpoint generator is present, which specifies a high generator current for the case that the tissue impedance at the probe is low-resistance at the beginning of the cut. Another advantageous embodiment consists in the fact that a setpoint generator is provided which, in the event that the tissue imbalance at the beginning of the cut A high generator voltage specifies high impedance at the probe.

By timely detection of different materials, in particular metallic parts in the vicinity of the cutting electrode, the power can be reduced to a non-hazardous value at which cutting is no longer possible and there is no risk of coagulation. Alternatively or additionally, the surgeon can also be warned.

For this purpose, the high-frequency generator has, according to the invention, a display device which compares the spectrum of the power at the output of the generator, which is influenced by the arc, or a quantity dependent thereon, such as current or voltage, in at least two different frequency ranges. In accordance with the result of the comparison, a setpoint is given which influences the performance of the generator. Differences in their electrophysical properties are used here to characterize different materials. These have a strong effect on the arc which arises during cutting in high-frequency surgery between the cutting electrode and the tissue. This bridges the vapor layer between the electrode and the tissue created by the evaporation of cell fluid. This arc does not burn evenly over the entire surface of the cutting electrode. Provided that the voltage is sufficiently high, it will ignite where the vapor layer is thinnest. The strong energy concentration caused by the arc ensures that the cells evaporate quickly at the point of transition. A stronger vapor layer now forms here and the arc moves to another location with a smaller insulation distance. The different materials of the cutting tool and material to be cut are characteristic of a typical cutting process. The principle is explained in the following by way of example for the case of a tissue trimming with a metal electrode, which occurs frequently in practice. Metal and tissue have different physical properties such as the work function of the electrons. This effect is reinforced by the different temperatures of the materials. Because of the evaporation of the cell liquid contained therein, the tissue will initially not assume any temperatures above the boiling point of the cell liquid. The ignition and burning voltages of the arc thus differ depending on whether the metal currently has the more negative potential or the tissue has the more negative potential. With metal as the cathode, the ignition voltage is lower than with tissue. Thus, when a high-frequency alternating voltage is applied, the current flow begins at different times depending on the polarity. This asymmetry can be measured by a spectral evaluation. Depending on the combination of cutting electrode and material to be cut, a characteristic spectral power distribution is therefore established.

If a structure made of another material is so close to the cutting electrode that the arc jumps over it, the different electrical properties of the materials change the symmetry of the current flow and thus also the spectral power distribution in the output signal of the generator. An evaluation of the different spectral power distribution is possible by comparing at least two non-identical frequency ranges.

By evaluating the spectral power distribution different materials can be differentiated. A typical example is the distinction between woven and metallic conductive structures. Several types of tissue can also be distinguished from one another by a more detailed evaluation. Knowing the material enables the generator power to be adapted to the conditions at the operating site. In this way, the generator can be switched off immediately before contact with metallically conductive structures in order to avoid coagulation of the surrounding tissue.

Tissue differentiation can e.g. in a prostate section only the adenoma tissue is removed. Cuts in the capsule that would result in perforation can be prevented.

A particularly advantageous embodiment is described below. In materials with similar electrical properties, the arc predominantly produces odd-numbered harmonics of the generator frequency, while with different electrical properties, the even-numbered harmonics of the generator frequency predominate. With the same materials, only odd-numbered harmonics of the generator frequency occur. The term "harmonic" is understood here to mean the multiples of the generator frequency, including the harmonic of the 0 th order, which corresponds to the DC component (f = 0). Therefore, a particularly advantageous embodiment consists in that two filters for evaluating the spectral components of the generator signal are present in the display device and the first filter predominantly detects the spectral power at one or more of the odd harmonics of the fundamental frequency of the generator fo and the second filter predominantly the spectral power with one or more even number gene harmonics of the fundamental frequency of the generator fo detected. This embodiment can be used particularly well for the detection of metallic structures in the tissue.

For the detection of different materials, an auxiliary oscillator signal of low power with the frequency f H can be additively superimposed on the generator signal with the frequency f o. The nonlinearity of the arc produces distortions and thus higher order mixed products. In the case of similar materials, second-order mixed products with the frequencies 2 fo, 2 f H, fo + f H, fo-f H predominantly arise, while in the case of different materials, the third-order mixed products with the frequencies 3 fo, 3 f H, 2 fo + f H, fo + 2 fH, 2 fo - f H, fo - 2 f H, f H + fo - fo arise.

Therefore, a further advantageous embodiment consists in that an auxiliary oscillator signal of low power is additively superimposed on the generator signal. In the evaluation, one or more of the second-order mixed products are detected by the first filter and one or more of the third-order mixed products by the second filter. Such methods are particularly advantageous if the generator is not sufficiently harmonic-free, or if the generator frequency is not sufficiently stable, so that filtering out the harmonics would require a great deal of effort.

A particularly advantageous embodiment for using the information obtained about differences in the tissue or other materials is to use this to regulate the generator power or to greatly reduce the generator power, so that no cutting and / or no coagulation of the tissue is possible. Another embodiment is a warning device that warns the user of the high-frequency surgical generator. The user can then recognize dangerous conditions and, for example, choose a different cut, switch off the generator, replace faulty surgical instruments.

A reduction in the generator power is advantageously controlled via a timing element, so that after the detection of a certain tissue or other material, the power of the generator remains reduced for a predetermined time. In this way it is avoided that an unnecessarily high power is supplied to the tissue by increasing the generator power too often, because after the generator power has been reduced no arc occurs by definition and the display device can no longer recognize the tissue or material. Without a timer, the power would be increased again immediately after the power reduction. The time of the timer can last a half wave, but it can also be much longer. For special applications, it can make sense to only enable generator activation when a new cut is made.

In addition, monitoring of the tissue impedance can be installed. It detects jumps in impedance, e.g. occur when removing the cutting electrode and then ends the time interval of the timer.

A high-frequency generator for high-frequency surgery, which can be controlled in order to minimize the disturbance of other devices or the irritation of certain muscles and nerves in its output power or an electrical quantity dependent thereon, has a blanking device with the aid of which the output power of the generator is reduced can.

Depending on the application, the generator can have no, one or more controls for its output variables. According to the invention, the blanking device is controlled by a measuring device for determining times to be protected. As a result, the output power of the generator is reduced or even completely switched off at these times, so that the disturbances caused directly or indirectly by the generator signal can be neglected. This also includes interference that occurs due to modulation and / or non-linear effects outside the generator. The arc represents a particular time-dependent non-linearity. Thus, during the times to be protected, no disturbances in other electronic devices or muscle and nerve irritations can occur. The time intervals in which the generator power is reduced can be longer, or can also have a time shift in relation to the time intervals determined by the measuring device to determine the times to be protected. This may be necessary, for example, to enable the series capacitor present in the generator output to be discharged in accordance with the VDE safety regulations. This can be charged during a cut by the constant component caused by the non-linearity of the arc. At the beginning of the time interval to be protected, the charge must also have flowed out of this capacitor in good time, since otherwise muscle and nerve irritations can also be caused by the discharge current. The time intervals should be chosen so large that the original operative goal does not change. The modulation of a generator signal primarily designed for cutting should not result in a predominantly coagulating effect. Furthermore, the generator has a device for determining the internal states after the time intervals in which the generator power is reduced. In this way, setpoints and settings for the following time interval can be specified for the internal circuit parts of the generator and its control and regulating devices. These can be preset or variable and allow adaptation to the surgical goal.

A characteristic of regulators, such as those used in HF surgical generators, is their time constant, which must be substantially greater than the period of the generator frequency. In the case of a cut with periodic interruptions, these controllers would have to settle in at the beginning of each cutting interval. This can lead to coagulation. As a result, the cut quality deteriorates. It is characteristic of a cut with such short interruptions, however, that the physical properties of the tissue at the surgical site change only insignificantly during these short time intervals. It would therefore be possible to continue the cut with the same parameters of the generator setting. To this end, not only are the default values for the parameter settings stored, but also the internal states of the controllers are recorded.

A particularly advantageous embodiment is that the generator has a storage unit for storing all important parameters, in particular the states of the internal controllers. As an example, implementation with analog memories would be possible with analog controllers and implementation with digital memories for digital controllers. The values are saved at the end of the cutting interval at the beginning of the break. At the beginning of the next time interval at the end of the break

the time intervals to be protected are determined based on the heart rhythm of the patient. This can e.g. are derived from EKG signals. Particularly in the case of operations in the vicinity of the heart or in the case of pacemaker wearers, the power output of the generator can thus be limited to the times in which the heart muscle cannot be excited by electrical fields. This significantly reduces the risk of ventricular fibrillation.

Frequently, other devices are operated during high-frequency surgical operations, which make data transmission at a high data transmission rate necessary. In this way, data is transmitted between computers or other devices in digital or analog form. This can be measurement data or values that are displayed on a screen. For this purpose, these data can be derived from imaging systems of all kinds, such as ultrasound devices or X-ray devices. These data are further processed and recorded in computer systems or video processors. At certain times, falsifying these data can have particularly critical effects and significantly falsify their information content. An advantageous embodiment therefore consists in that the measuring device for determining the times to be protected particularly determines those time intervals in which the transmitted data is most susceptible to interference. This is e.g. the case when the data is transferred from a computer to the storage medium for offline evaluation.

Brief description of the drawings

The invention is described below without restricting the general inventive concept on the basis of exemplary embodiments. play exemplarily described with reference to the drawing, to which reference is expressly made with regard to the disclosure of all details according to the invention not explained in detail in the text. Show it:

1: basic circuit diagram of the high-frequency surgical generator for cutting tissues,

2: Exemplary representation of the increase in impedance at the beginning of the cut,

3: basic circuit diagram of the high-frequency surgery generator for performing tissue or material-dependent operations,

4: basic circuit diagram of the high-frequency surgery generator with additional devices for advantageous embodiments,

5: Exemplary representation of the spectral distribution of the generator power and exemplary filter curves,

6: basic circuit diagram of the high-frequency surgical generator with minimal negative effects on the environment,

Fig. 7: Exemplary representation of the synchronization to an EKG signal.

Description of an embodiment

1 shows the basic circuit diagram of a high-frequency surgical generator, with which undesirable side effects are largely reduced when cutting tissues become. The high-frequency generator 1 for high-frequency surgery has control devices for setting the instantaneous electrical output variables such as, for example, current, voltage and power. The high-frequency current required for cutting is introduced into the tissue via the probe 11 and exits the patient through the neutral electrode 12. The contact area of the probe 11 is considerably smaller than the area of the neutral electrode 12, so that the thermal effects on which the high-frequency surgery is based occur on the probe 11. A device 2 serves for the immediate and / or indirect determination of the cutting. This device can contain a transducer in the immediate vicinity of the probe. It can also contain an evaluation device for evaluating the electrical output variables of the generator. Optionally, the device for the direct and / or indirect detection of the cutting can contain a test signal generator 6, the test signal of which is fed to the probe and is measured with the aid of the measuring device 2. The measuring device can have a limit transmitter 7 which defines the threshold for the "cutting" state.

Furthermore, the device contains a setpoint generator 5 which, according to the output signal of the measuring device, specifies the setpoint value for the output power or another electrical variable proportional to the high-frequency generator.

2 shows the course of the tissue impedance at the beginning of a typical incision in the stomach or intestinal wall, as was determined in many measurements. First of all, because of the conductive liquid on the surface, the tissue impedance is very low. After sufficient energy was supplied to these rivers

Claims

P a t e n t a n s r u c h e

High-frequency surgical generator (1) for cutting tissues with control devices with which at least one of the current electrical output variables, such as Current, voltage, power or electric arc can be set, characterized in that an electronic setpoint generator (5) and a measuring device (2) with an evaluation unit for the indirect and / or immediate detection of the cutting are present to improve the cutting behavior and the electro¬ African setpoint generator (5) at the beginning of the cut specifies a generator setting that is particularly suitable for cutting until the measuring device (2) signals tissue-cutting cutting of the probe (11) and then specifies a lower setpoint for the generator so that a normal one , the cut corresponding to the desired surgical goal is made.

2. High-frequency generator according to claim 1, characterized in that a limit indicator (7) and a measuring device (2) with an evaluation unit for the indirect and / or immediate detection of the tissue-cutting is present, the measuring device (2) from the probe (11) distance covered in the tissue is determined, this distance is compared with the limit value from the limit value transmitter (7) and a signal "cutting" is displayed when the limit value is exceeded.

3. High frequency generator according to claim 1, characterized in that There is a limit indicator (7) and a measuring device (2) with an evaluation unit for the indirect and / or immediate detection of the tissue-separating cutting, which evaluates the arc occurring on the probe (11), compares it with the limit value from the limit indicator (7) and at If the limit value is exceeded, a "cutting" signal is displayed.

4. High-frequency generator according to claim 1, characterized in that a limit value transmitter (7) and a measuring device (2) with evaluation unit for indirect and / or immediate detection of the tissue-separating cutting vor¬ are present, the impedance between the probe (11) and Evaluates the neutral electrode (12), compares it with the limit value from the limit value transmitter (7) and displays a "cut" signal when the limit value is exceeded.

5. High-frequency generator according to one of claims 1 to 4, characterized in that a setpoint generator (5) is present, which at the beginning of the cut with low impedances of the tissue on the probe (11) specifies a high generator output until the measuring device (2nd ) displays a "cutting" signal.

6. High-frequency generator according to one of claims 1 to 4, characterized in that a setpoint generator (5) is present which at the start of the cut with high impedances of the tissue on the probe (11) specifies a high generator voltage until the measuring device (2nd ) displays a "cutting" signal.

7. High-frequency surgical generator (1) with a device for adjusting one of the tissue or material samples. adequate maximum output power at the operating site, characterized in that a display device (3) is present which compares the arc-influenced spectrum of the power at the generator output or a quantity dependent thereon such as current or voltage in at least two different frequency ranges, which power contained therein indicates as an electrical signal, and that there is an evaluation circuit (4) which is supplied with the output signals of the display device and which contains a setpoint generator (5) which, depending on the ratio of the output signals of the display device, has a setpoint value for specifies the setting of the high frequency generator.

8. High-frequency generator (1) according to claim 7, characterized in that in the display device (3) there are two filters for evaluating the spectral components of the generator signal, the first filter (8) predominantly the spectral power at one or more of the even-numbered harmonics ¬ the fundamental frequency of the generator fo is detected and the second filter (9) predominantly detects the spectral power at one or more odd-numbered harmonics of the fundamental frequency of the generator fo and that the setpoint output by the evaluation circuit is controlled by the setpoint generator (5) so that the power of the high frequency generator is reduced, and / or optionally a warning device (10) is present which is actuated when the ratio of the odd harmonics of the basic frequency of the generator fo to the even harmonics of the basic frequency of the generator fo exceeds a preset value. 9. High-frequency generator (1) according to claim 8, characterized in that additionally an auxiliary oscillator (13) with low power and the oscillator frequency f H and a coupling element (14) for additive superposition of the auxiliary oscillator signal to the output signal of the high-frequency generator (1) are provided, wherein the first filter (8) mainly detects signals that arise from even-numbered order distortions, and that the second filter (9) mainly detects signals that arise from odd-order order distortions.

10. High-frequency generator (1) according to claim 8 or 9, characterized in that one of the filters (9) is designed as a low-pass filter and predominantly transmits the low-frequency components by the frequency 0 Hz.

11. High-frequency generator (1) according to one of claims 7 to 10, characterized in that the setpoint generator (5) is additionally coupled to a timer (18) which reduces the power of the high-frequency generator for a predetermined time interval between a minimum time corresponds to the duration of a half-wave of the HF signal from the high-frequency generator (1) and increases a maximum time until the switch (15) is opened to activate the generator

12. High-frequency generator (1) according to claim 11, characterized in that a device (16) for determining the impedance of the tissue is present in the display device (3) and this device (16) is coupled to an impedance evaluation circuit (17), which at exceed a preset set impedance limit value, the time interval in which the power of the high-frequency generator is reduced is canceled.

13. High-frequency surgical generator (1), which is controllable in its output power and has a Austasteinric device (18), characterized in that a blanking device (18) with a blanking frequency of up to 1000 times per second is present, the generator line being at time intervals , which are predefined by a device (19) for determining times to be protected from generator power, is reduced in such a way that the disturbances caused by the generator power can be neglected, and that a device (22) is provided for fixing the internal ones States of the generator after the time intervals in which the generator power is reduced.

14. High-frequency generator according to claim 13, characterized in that a setpoint generator (5) is present which, after the time interval in which the generator power is reduced, setpoints for setting the output power and / or other variables for internal states of the generator specifies which were determined as standard values for the respective operation task for the following time interval.

15. High-frequency generator according to claim 13 or 14, characterized in that a memory unit (20) with a trigger device is present for storing the settings and internal states of the generator, and that by the output signal

There is a signal (21) from data processing systems and the device (19) for determining the times to be protected derives time intervals for reducing the generator power from them so that at times when a malfunction affects the effect of the System particularly affected, the interference caused by the RF power in the data processing systems is minimal.

19. High-frequency generator according to claim 1, 7 and 13, characterized in that the devices for improving the cutting behavior, the tissue- or material-dependent operation and the minimization of interference to the environment are combined with one another and matched in one device.